A chip scale camera module (CSCM) is known for a compact camera module used in portable telephones, and the like. The CSCM has a lens holder, in which a lens is directly incorporated inside, fixed on a solid state imaging device in a focused state with an adhesive applied onto the solid state imaging device.
The solid state imaging device includes a thinned silicon substrate having a sensor chip at a central part of the front surface, and a glass substrate fixed on the silicon substrate. External electrodes are formed on the back surface of the silicon substrate. The external electrodes are electrically connected to the sensor chip through a through-electrode formed on the silicon substrate using the TSV (Through Silicon Via) technique. The CSCM is mounted on a mounting substrate through the external electrodes.
However, a gap is formed between the mounting substrate and the back surface of the solid state imaging device when the CSCM is mounted on the mounting substrate. The light reflected at the front surface of the mounting substrate thus passes through the gap and enters the back surface of the solid state imaging device. The silicon substrate of the solid state imaging device has a property of transmitting infrared light. Therefore, the infrared light component of the light that entered the back surface of the solid state imaging device is transmitted through the silicon substrate and reaches the sensor chip. The infrared light is received by the sensor chip as a noise component. Therefore, the image output from the CSCM degrades.